Device for resisting movement of the arm of a drill



. Deg. 26, 1944. w. e. HOELSCHER DEVICE FOR RESISTING MOVEMENT OF THEARM OF DRILLS Filed Sept. 29, 1941 ATTORNEYS v Patented Dec. 26, 1944DEVICE FOR RESISTING MOVEMENT, OF THE i ARMOFADRILL William Hoelscher,Cincinnati, Ohio, assignor to The American Tool Works Company,Cincinnati, Ohio, a corporation of Ohio Application September 29,1941,Serial No. 412,768

p p p 1 Claim.

This invention relates to machine tools and is particularly directed toimprovements in radial drills. More particularly, the invention isconcerned with improvements relating to the control of the arm"movement.

In certain types of Work, such as for example, where a number of holesare to be drilled in a piece of work, considerabletime is lost inclamping and unclamping the arm. In all radial drillstructuresgheretofore known, the arm is "arranged to swing freely; thatis, it may either swing on the column or it may swing as a unit with thecolumn on a stump. A clamping de-' vice is provided for fixing the armin a selected position so that the spindle is in registry with the holeto be drilled, whereby the arm cannot swing during the drillingoperation; Where smaller holes are to be drilled and the drillingthrustis not greatQit has been the practice to perform the drilling,operations without clamping the arm, but this is not efiicient, fordisaligned or otherwise inaccurate drilling is apt to result.

Accordingly, it has been the object of the present inventor to providean improved structure wherein a predetermined amount of resistance maybe applied to the arm for holding it in position against displacementunless a, certain amount of pressure-is applied to the arm. In otherwords, the purpose here has been to provide a resistance means inconnection with the arm for holding the arm relatively fixed, but notimmovable, in the drilling position.

As a result of this improvement, it is possible for the operator todispense with the use of the normal clamping means; that is, the onewhich fixes the arm against any movement, and utilize iective upon thecolumn for tighteningit around i the stump, thereby creating africtional fit between them. In thosecases where the arm rotatesdirectly on the column, the same tightening principle may be employedfor tightening the arm directly upon the column.

Other objects and certain advantages of the invention will be more fullyapparent from a description of the drawing in which:'

Figure 1 is a perspectiveview of a radial drill incorporating thepresent invention.

Figure 2 is a fragmentary side view of a portion of the drill showingthe lever for the device of the presentinvention for applying aresistance to column movement relative tothe stump.

Figure 3 is a fragmentary side view partially in section, taken at rightangles to Figure 2 for illustrating the relationship of the resistanceapplying means and the normal clamping means:

Figure 4 is a sectional view taken on line 4--4, Figure 3, detailing theresistance applying means.

Figure 5 is a sectional View taken on line 5-5,

Figure 3, illustrating the limit stop means fo r the normal clampingdevice. l

For the purpose of illustrating the invention, an otherwise conventionalradial drill has been depicted. The radial drill disclosed is of thetype in which the arm and column rotate as a unit and accordingly, theresistance device is placed on the column for action thereon to set up apredetermined drag or resistance on the stump. In general, the device isarranged so as to provide an easily accessible handle operating atightening means incorporating an adjustable stop so that the amount ofdrag or resistance may be predetermined.

Referring to the drawing, the base of the radial drill is indicated atl0 and includes a stump member indicated at H. The column is indicatedat l2, the arm at l3, and the head at I4. It is not considered necessaryto describe in any way the details of the drill other than the structureat the base of the column, at which point the device of the presentinvention is illustrated.

The column includes the usual enlarged base portion I5 fitted over thecounter-turned portion It of the stump. A thrust bearing I! is dis posedon the shoulder I8 of the stump and bears the weight of the column byengagement within the internal shoulder IQ of the column. This enlargedportion of the column is inclusive of a split section providing slightlyspaced radially extended portions 20 separated by the split and furtherrendered flexible by means of a circumferential slot 2| in the portionl5 of the column just above the radially extended portions andintersected by the vertical split;

Generally described, the normal clamping means consists of an arm 22having a pivotal abutment with one section through an element 23 andswung on this abutment by means of a cam 24 fixed on a shaft 25.mountedon the column base. A draw bolt 26 traverses the radially extended splitportions and the pivoted end of the arm. This draw bolt includesabutment elements at each end. The effect of outward swinging-movementof the arm 22 is to pull the portions 2|] together to clamp the base ofthe column on the stump. A lever 2'! rotates the shaft through anothershaft 28, and bevel gears 29-29. ing movement of the shaft 25 is limitedby means of a stud 30 adapted to engage limit stops 3 l 3l fixed to thebase of the column.

The resistance device of this invention, in the preferred embodiment, islocated adjacent the main clamping lever 21. In, the present disclosure,it is located just beneath the shaft 28 and consists of a rotatablymounted shaft 34 journalled inan outer casing, wall 35 of the columnandiin one clamping portion 20; The. shaft 34 extends across the splitand has ascrew threaded portion projecting into a; screw threaded bore36 of the other split portion 2.0. The. shaft 34 includes a: shoulder 31lying; against; a shoulder within the bore of the splitportion 2|],whereby rotation. of the shaft in one direction'will, through thescrew;threads,.tightenthe1 split portions upon the stumpand. in: the,other direction will loosen them.

Anoperating lever: or" arm- 38 is; fixed tothe outerrend of the-shaftedand depends therefrom (Figure 2). Thislever includes-a manipulating knob39. at its lower end. It islimited in. its swinging movement by means ofa fixed stop 40 andan adjustable stop Ma The fixed. stop consists of ascrew engaged into. the outer' surface of the casing wall- 35;.The-adjustable stop consists of a plate 42' having a slot t3: thereintraversed by afastening screw 44; engaged through the slot inbothe'casing wall 35; The slot; extends at.v right. angles: to: the end ofthe: plate. to be As shown'in- Figure 5,; the clamp?- abutted by thelever and thus, the position of against accidental or easy movement andmakes it necessary to'apply a certain amount of pressure against the armbefore it can be moved to another drilling position. By using theadjustable plate, the operator can set the resistance I to the exactamount required for efficient operation.

, The adjustable. stop plate 42 is mounted so that it has a fair rangeof adjustment but in no event can it be moved far enough away fromthefixed stop 40 to permit movement of theresistance applying leversuflicient to lock the column in position. Asa. matter offact, theresist.- ance: applying means is not constructed for applying aclamping. or. looking pressure.

eration is supplemental to the operation of the normalclamping lever.

Having described my invention, I claim:

-In a radial drill, a base presenting'a stationary member; an arm,meansv for mounting. said arm relativeto said base; means for clampingsaid arm; against relative movement; including a. contractible' memberfor engaging said; stationary member, means. including. a lever forcausing a; partial contraction. of said. contractible member'iwhereby ayieldable resistance to r'otat-ive movement of said arm is provided, andpositive adjustable stop means operable in conjunction with said leverfor limiting the degree'of saidpar tial contraction whereby manipulationof said lever to said stop means provides a predetermined; drag againstrotativemovement for said arm.

WILLIAM G. HOELSCHER.

